1. Field of the Invention
This invention relates to reflection-type projection screens. More particularly, the invention relates to reflection-type projection screens having excellent reflection directivity in the horizontal and vertical directions yet which produce a reflected image having superior gain contrast.
2. Description of the Prior Art
The desirability of producing reflection-type projection screens having a wide angle of reflectivity with suitable contrast is well known. In settings such as movie theaters and home viewing areas, the viewer is often times positioned at a significant angle with respect to the direction of the projected image from the projector, i.e. the direction of incident projected light. Therefore, the screen must have an effective viewing angle greater than would be producible if a reflective medium were used alone.
Numerous attempts have been made to remedy this problem. U.S. Pat. No. 3,653,740 to Ogura (xe2x80x9c""740 Patentxe2x80x9d) discloses a projection screen having a double rolled aluminum foil sheet attached to a support member, and a brushed resin film covering the foil as a protective coating against scratching, fingerprints, etc. No mention is made of the brushing techniques used or of the resulting surface characteristic of the resin film after it is brushed.
U.S. Pat. No. 6,144,491 to Orikasa (xe2x80x9c""491 Patentxe2x80x9d) discloses a reflection-type projection screen having a substrate, a light reflecting layer made from a transparent resin in which flakes of a light-reflective material are dispersed, and a transparent light-diffusing layer made from a transparent resin in which fine crystalline particles of calcite and a pigment are dispersed. The films of ""491 Patent are complicated, expensive and particularly difficult to achieve.
U.S. Pat. No. 6,040,941 to Miwa (xe2x80x9c""941 Patentxe2x80x9d) discloses a reflection-type projection screen having a light-reflecting substrate laminated to a light-transmitting polymer layer having light absorptive slits or xe2x80x9ccrazesxe2x80x9d of regular directionality disposed therein. The slits are filled with a light-absorbing substance such as a black pigment or dye.
U.S. Pat. No. 6,233,095 B1 to Niwa (xe2x80x9c""095 Patentxe2x80x9d) discloses a reflex-type screen comprised of a first layer formed integrally with an inner reflex layer on a surface of a substrate, and a second layer formed of a deflection film bonded to a surface of the first layer. The screen of the ""095 Patent was developed to facilitate the use of screens which can be deflected, e.g. rolled up when not in use. Beads such as acrylic or silicon beads are applied to the substrate surface prior to deposition of a metal reflective layer, rendering the process of attaching the metal reflective layer all the more complicated.
U.S. Pat. No. 5,456,967 to Nezu (xe2x80x9c""967 Patentxe2x80x9d) discloses a reflection-type screen of the type that can be wound up in a roll form and unwound as needed and comprises a substrate sheet to which is laminated a high-density light diffusion-reflection layer and a translucent light diffusion layer including a soft vinyl chloride sheet, the translucent light diffusion layer having a surface provided with a light-diffusing fine uneven pattern.
U.S. Pat. No. 5,361,163 to Matsuda (xe2x80x9c""163 Patentxe2x80x9d) discloses a reflection-type projection screen comprising a dark plastic substrate, a fibrous sheet of glass fibers, a white, opaque base material sheet and a light diffusing layer of a translucent plastic onto which a lustrous pigment or calcite powder is incorporated. An emboss is formed on the outer surface of the light diffusion layer. Light absorbing strips are provided each at a position corresponding to a concave portion of the emboss on the surface of the base material sheet adjoining the light diffusing layer.
U.S. Pat. No. 5,148,309 to Yamada (xe2x80x9c""309 Patentxe2x80x9d) discloses a reflective type screen comprising a reflective surface layer, a polarizing plate layer in position in front of the reflective surface layer, and a diffusion layer located in front of the polarized plate layer, wherein the reflective surface layer, the polarizing plate layer and the diffusion layer are laminated together using an adhesive to form an integral structure. Additional embodiments are disclosed in the ""309 Patent, all of which require a polarizing layer, perhaps to accommodate exotic applications of projection images onto a screen.
U.S. Pat. No. 4,232,939 to Kikuchi (xe2x80x9c""939 Patentxe2x80x9d) discloses a transparent base plate to which is attached on one side an aluminum mirror surface and on the other side a diffusing specular layer of low diffusing performance. The diffusing performance of the diffusing specular layer can be adjusted as desired while the reflection performance of the mirror surface is constant. The diffusing specular layer is formed with a plurality of elongated columnar lenticles having convex surfaces facing the viewer. The curvature of the lenticles is determined by the distance between the screen and the viewers. The outer convex surface of the lenticles is treated by sandblasting. The lenticles are arranged in a vertically elongated pattern, which sacrifices vertical directivity.
U.S. Pat. No. 4,201,449 to Campion (xe2x80x9c""449 Patentxe2x80x9d) teaches a front projection screen having a substrate, a reflective aluminum ink coating applied to a surface of a substrate, and a protective coating, preferably of a clear acrylic having a gloss finish for the purpose of protecting the reflective film. The disclosure specifies that the coating reduces somewhat the reflective efficiency of the screen. Therefore, the directionality of such a screen is likely to be extremely narrow.
U.S. Pat. No. 4,190,320 to Ferro (xe2x80x9c""320 Patentxe2x80x9d) teaches a front projection screen having two reflecting layers separated by a light transmissive layer, and a light-diffusing surface coating provided on the frontmost reflecting layer. The screen forms an embossed pattern across its front surface.
U.S. Pat. No. 4,089,587 to Schudel (xe2x80x9c""587 Patentxe2x80x9d) discloses a projection screen having a film which is constructed of a partially deformable, resilient material. One surface of the film has in combination a random matte texture and a substantially unidirectional striated, i.e. grooved, texture. A layer of reflective material is deposited on the above-mentioned surface of the film to provide a high gain, damage resistant reflective surface. The screen of the ""587 Patent is intended to be of the double-coverture type, i.e. curved about at least two axes so as to focus the reflected image in a confined area. Another embodiment of the ""587 Patent discloses a flat screen. Striations are provided, usually vertically aligned to disburse the light reflected off of the reflective film. The arrangement of the striations or lenticles as vertical grooves limits the directionality to nearly a side by side viewing field and not top to bottom or diagonal.
It is therefore, an object of this invention to provide a front projection screen which overcomes the aforementioned disadvantages and shortcomings.
It is also an object of this invention to provide a front projection screen which provides the same directionality, i.e. directivity, along vertical as well as horizontal axes relative to a normal line passing perpendicularly through the center of the projection screen.
It is a further object of this invention to provide a projection screen which is simple and inexpensive to manufacture and light weight yet which provides directivity characteristics not heretofore experienced.
In accordance with these and other objects, the invention is directed to a projection screen comprised of a reflective film laminated, as by the use of adhesive, metal deposition, or otherwise as will occur to those of skill in the art, to a light diffusing layer on one side and, on another side, as by adhesive, metal deposition, or other techniques known to those of skill in the art, to a substrate. The substrate may be rigid or flexible, flat or curved.
The reflective film may be vacuum metalized silver or vacuum metalized aluminum or any other film exhibiting a high coefficient of reflectivity. The characteristics of the light diffusing layer can be adjusted depending upon the desired effect, intensity of projected image light, ambient conditions, etc. One form of the diffusing layer is an embossed film. One form of such embossed film contains a plurality of concavities embossed in the film which act as micro lenses. The surface characteristics, e.g. concavities, associated with the light diffusing layer can be formed by techniques such as hot roll stamping, ultra etching or the like.
The reflective layer may be adhered to the substrate or to the substrate-facing inner surface of the light diffusing layer.
It can therefore be appreciated that one embodiment of the invention is to a projection screen comprising a substrate having a generally flat forward surface; a diffusion layer formed of a plurality of generally equally spaced apart concave features forming micro lenses; a layer of reflective material deposited on a rearward facing surface of the diffusion layer; the diffusion layer laminated to the forward facing surface of the substrate so that the layer of reflective material is sandwiched there between.
These and other objects and features of the invention will be more readily understood from a consideration of the following detailed description, taken with the accompanying drawings, in which corresponding parts are indicated by corresponding numerals.